The invention relates to an apparatus for producing a multilayered film composite comprising sealed-together plastic films, said apparatus having a number of supply rolls, on which the plastic films in web form are wound, as well as to a process for producing a multilayered film composite from biaxially stretched and/or monoaxially stretched and/or unstretched thermoplastic, coextruded plastic films, which are provided on at least one side with a sealing layer, by sealing the films under pressure and heat application.
On the part of various industries, such as for example apparatus engineering, vehicle and aircraft engineering, or safety technology, there is an increasingly great interest in high-strength film composites and composite bodies in the form of webs and semi-finished products, such as for example sheets, as well as finished components. Following this trend, sheet producers are working on techniques for the production of products which can be subjected to higher mechanical loads. At the same time as modification of the polymer materials intended for sheet production by the incorporation of reinforcing materials, such as for example textile, glass, or carbon fibers, techniques for the production of intrinsically reinforced sheets by orienting measures are being developed. Examples of solutions covered by these techniques are roll press stretching or the process described in EP-A 0 207 047, the essential measure in the process being that of compressing a plurality of biaxially stretched films, provided with thin, coextruded sealing layers, into a homogeneous sheet of any thickness, with application of pressure and heat. For this purpose, in general the stack of films laid between two pressing plates is introduced into discontinuously operating, hydraulic plate presses of single or tier design. The pressing operation is determined by process parameters, such as pressure, temperature, and time. The last of these process parameters in particular stands in the way of inexpensive production of composite laminates, in particular in the case of heating through very thick panels. Continuous run-through presses, in particular twin-belt presses, represent a practicable, time-saving solution in this respect, but can only be used to a limited extent in view of the speeds which can be achieved on them.
German Patent 35 30 309 describes a process and an apparatus for continuously producing thermoplastic webs, in particular for further processing into panels or films, from at least one extruded thermoplastic web heated to processing temperature, which in the heated state is cooled between two fixedly arranged pressure plates, so that the surface of the thermoplastic web is calibrated and smoothed. The cooling of the thermoplastic web is performed under the action of surface pressure, for which purpose it is guided during cooling between two continuously moving, endlessly circulating pressing belts. At the same time, a uniform surface pressure is exerted from the pressure plates hydraulically or mechanically on the inner sides of the moving pressing belts and is transferred from these to the thermoplastic web. The pressure plates are kept at a lower temperature than the final temperature of the thermoplastic web, in order in this way to maintain a temperature gradient between thermoplastic web, pressing belt, and pressure plate. The cooling of the thermoplastic web takes place by heat from the web being dissipated via the pressing belt to the pressure plates by means of heat conduction. The surface pressure acts throughout the entire duration of the cooling of the thermoplastic web between the pressing belts.